JP2000321260A - Analyzer for fuel gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an analyzer in which a calolific value can be measured at high speed and with high accuracy by using a chromatograph. SOLUTION: In a first analytical part 11, a component C3 or higher is excluded by a precolumn PC1, a valve V2 is changed over at a prescribed timing, oxygen, nitrogen and methane are separated by an MS-5A column MC2, and carbon dioxide and ethane are separated by a polymer bead column MC3. On the other hand, in a second analytical part 12, a component C6 is excluded by a precolumn PC2, and the component C3 to a component C5 are separated by an alumina plot column MC4. When the step-up control of the entrance pressure of the column MC4 is used jointly, a GC analysis can be finished within about 3 minutes. The concentration of every component is calculated by the GC analysis, it is multiplied by the correction factor of a heat quantity, its total sum is calculated, and a calolific value is found. The concentration of components other than a component, to be analyzed, which contains the component C6 is estirrsated in such a way that the pressure of the concentration of every component obtained as a result of the GC analysis is corrected and that the concentration is estimated from the deviation amount of the total sum of the corrected concentration from 100%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition analysis of various fuel gases such as city gas and power generation gas produced from liquefied natural gas or the like using a gas chromatograph, and based on the result, a total heat generation. The present invention relates to a fuel gas analyzer that calculates an index value indicating the performance of a fuel gas such as an amount.

[0002]

2. Description of the Related Art City gas supplied to ordinary households and factories is prepared using liquefied natural gas as a main raw material. In order to determine the performance of such fuel gas including city gas, index values such as the total calorific value, Wobbe index, combustion speed, and combustion capacity are used.

[0003] The total calorific value of the fuel gas can be determined by actually burning the fuel gas and measuring the combustion heat using a flame calorimeter or the like. And the total calorific value can be calculated from the result. Conventionally, as a method of quantitatively analyzing and testing such fuel gas, Japanese Industrial Standards (JIS) K2301 “Analysis and analysis of fuel gas and natural gas
Standards based on the “test method” and the GPA method are known.

[0004] For example, according to the above JIS standard, a gas chromatograph is used for quantitative analysis of general components (methane and other hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and nitrogen, etc.) contained in fuel gas. Done. In this analysis, the hydrocarbons are those having a carbon number of 1 (that is, methane) to 6 (hexanes).
Since it is impossible to properly separate all of these components using one type of column, hydrocarbons having 3 to 6 carbon atoms (hereinafter, hydrocarbons having n carbon atoms are referred to as “Cn”) are used. For separation, a column such as sebaconitrile or DOP (dioctyl phthalate) is used. For separation of other components, MS-
A 5A (synthetic zeolite) column and a polymer bead column are used. In the GPA method, a DC-200 (silicone grease) column is used for separating components of C3 or more.

[0005] The concentration of each component can be calculated by analyzing the chromatogram obtained by the gas chromatograph apparatus. However, gas sampling is performed by the difference between the atmospheric pressure during standard gas analysis and the atmospheric pressure during sample gas analysis. Variations in volume can result, resulting in fluctuating absolute concentrations. Therefore, the final analysis value of each component is calculated by normalizing the sum of the concentrations of each component to be 100%.

[0006]

In order to maintain a certain level of accuracy by the above-mentioned conventional analysis method, it is necessary to use a method of 15 to 15 degrees.
An analysis time of about 40 minutes was generally required. This is mainly due to the long time required to separate the C3-C6 components from each other in the column. When the frequency of the measurement of the total heat generation is not high, it does not matter much if the analysis takes a certain amount of time. However, for example, in an application in which the total calorific value of city gas supplied through a pipe is monitored with high frequency, the analysis time is shortened as much as possible, and the analysis time is shortened within several minutes at most. There is a need for an analytical method.

[0007] The present invention has been made in view of such a point, and an object of the present invention is to significantly shorten the analysis time as compared with conventional analysis, and to obtain sufficiently high analysis accuracy. It is to provide a fuel gas analyzer which can be used.

[0008]

The fuel gas analyzer according to the present invention, which has been made to solve the above-mentioned problems, comprises: a) a gas chromatograph for measuring the concentration of each component of the fuel gas; and b) a fuel gas. Pressure correction means for measuring the atmospheric pressure at the time of analysis, and correcting the dependence of the concentration of each component obtained by the gas chromatograph on the sample gas introduction amount depending on the difference between the atmospheric pressure and the atmospheric pressure at the time of standard gas analysis. C) estimating means for estimating the amount of the component other than the analysis target based on the sum of the analysis values of each component corrected by the pressure correcting means, and d) analysis value of each component corrected by the pressure correcting means And a calculation means for calculating an index value relating to the performance of the fuel gas by performing a predetermined calculation process on the gas chromatograph, wherein the gas chromatograph comprises: a1) a hydrocarbon component having 3 to 5 carbon atoms and other general components. And A sample introduction system for introducing a sample gas into a measuring tube independently provided for performing each analysis in parallel, a2) a pre-column for excluding hydrocarbon components having 3 or more carbon atoms, and a pre-column. A3) a first separation section including a column for separating each of the excluded components; a3) a precolumn for removing hydrocarbon components having 6 or more carbon atoms; and a precolumn for removing hydrocarbon components having 3 to 5 carbon atoms. It is characterized by having an alumina plot column for separation and a second separation unit including a pressure control means for increasing the column inlet pressure in a predetermined sequence.

Liquefied natural gas and certain types of synthetic natural gas are
It does not contain a hydrocarbon component having 6 or more carbon atoms (C6 + component), or it contains a very small amount. Therefore, in the gas chromatograph of the fuel gas analyzer according to the present invention, in the second separation section, the C6 + component which has been conventionally analyzed is collected using a pre-column and removed from the sample gas introduced into the main column. . Also, C3, C
4. As a column for separating the C5 component, an alumina plot capillary column is used, and the pressure is controlled to gradually increase the inlet pressure, thereby allowing each component to flow out of the column in a short time while being sufficiently separated. . As a result, when C3, C4, and C5 components are separated by a DC-200 column, those requiring 15 minutes or more can be separated within about 3 minutes.

In the fuel gas analyzer according to the present invention, the other general components may be hydrogen, oxygen, nitrogen, methane, carbon monoxide, carbon dioxide, and ethane.

In the fuel gas analyzer according to the present invention, the first analyzer separates hydrogen, oxygen, nitrogen, methane, and carbon monoxide from carbon dioxide and ethane in advance, and further separates them. It is possible to adopt a configuration in which each component is separated by a column. Specifically, a column using synthetic zeolite as a separation phase is suitable for separating the former components, and a column using polybeads for the separation phase is suitable for separating the latter components.

Further, the index values obtained by the fuel gas analyzer according to the present invention include the total calorific value, the Wobbe index, the burning speed, the burning capacity, and the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel gas calorific value measuring apparatus according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the fuel gas calorific value measuring device of the present embodiment.

This fuel gas calorific value measuring apparatus includes a gas chromatograph analyzing section (hereinafter, referred to as a "GC analyzing section") comprising a plurality of columns and a valve for switching a flow path, as described later.
1), a quantitative analysis unit 4 that creates a chromatogram based on the detection signal obtained from the detector 2 of the GC analysis unit 1 and analyzes the chromatogram to calculate the concentration of each component. Atmospheric pressure monitor 8 for measuring atmospheric pressure
A pressure corrector 5 for correcting the concentration of each component in accordance with the atmospheric pressure measured by the atmospheric pressure monitor 8, standardizing the pressure-corrected concentration, and formulating a predetermined arithmetic expression based on the standardized concentration. The apparatus includes a calorific value calculating section 6 for calculating a total heat generation value by using it, and another component estimating section 7 for estimating the concentration of a component not to be analyzed based on the pressure corrected concentration.
The data processing unit 3 including the quantitative analysis unit 4, the pressure correction unit 5, the calorific value calculation unit 6, and the other component estimation unit 7 can be configured mainly with a personal computer or the like, and although not shown, an operation unit such as a keyboard or a display. And an output unit such as a printer.

FIG. 3 is a diagram showing the flow path configuration of the GC analyzer 1 in FIG. The GC analysis unit 1 is roughly divided into a first analysis unit 11 for mainly analyzing oxygen, nitrogen, methane (CH4), carbon dioxide (CO2), and ethane (C2H6), and C3, C4, C
It is divided into a second analyzer 12 for analyzing five components. FIG.
, The first switching valve V1 and the third switching valve V3
Is a 10-port 2-position valve, the second switching valve V2
Is a 6-port 2-position valve.

The configuration of the first analyzer 11 is as follows.
The sample gas inlet 13 to which the sample gas to be analyzed is supplied is connected to a port h of the first switching valve V1, and a first measuring pipe 14 is provided between the port g and the port j of the first switching valve V1.
Is connected. The port i of the first switching valve V1 is connected to the port h of the third switching valve V3.
A first switching valve is provided between port b and port f of the first switching valve V1.
The pre-column PC1 is connected, and the port e communicates with the exhaust port (VENT) via the first choke column CC1. Further, the first dummy column DC1 is connected to the port d, and the other end of the first dummy column DC1 and the port a are both connected to the outlet of the first pressure controller 15 for electronically controlling the supply pressure of the carrier gas. Have been.

The port c of the first switching valve V1 is connected to the port a of the second switching valve V2 via the first main column MC1.
And a port b and a port f of the second switching valve V2 are connected to the thermal conductivity detector (TCD) via the second main column MC2 and the third main column MC3, respectively.
It reaches the sample-side flow path 22. The port c and the port e of the second switching valve V2 are directly connected, and the port d is connected to the third dummy column DC3. The outlet of the second pressure controller 16 for electronically controlling the supply pressure of the carrier gas in the same manner as the first pressure controller 15 is connected to the other end of the third dummy column DC3 and is connected to the TCD 22 via the reference column RC1. Of the reference side flow path. The first and third main columns MC1, MC
3 is a polymer bead column, and the second main column MC2 is an MS-5A column.

The configuration of the second analyzer 12 is as follows.
Similarly to the first switching valve V1, a second measuring pipe 19 is connected between the port g and the port j of the third switching valve V3,
The second pre-column PC2 is connected between the port b and the port f, and the port e communicates with the exhaust port (VENT) via the second choke column CC2. Further, a second dummy column DC2 is connected to the port d, and the other end of the second dummy column DC2 and the port a are both connected to the third pressure controller 1
7 is connected to the outlet. Also, the third switching valve V3
Is connected to the fourth main column MC4, and the outlet thereof reaches a flame ionization detector (FID) 23. Further, a split flow path 21 having a flow path resistance is provided in a branched position in front of the entrance of the fourth main column MC4.
In addition, as the fourth main column MC4, a capillary column of an alumina plot is used.

The switching operation of the first to third switching valves V1 to V3 and the target control values of the first to fourth pressure controllers 15 to 18 are automatically controlled by a control circuit (not shown) as described later.

The operation of the GC analyzer 1 will now be described with reference to FIGS. 4 to 6 in the order of analysis. FIG. 4 is a flow path configuration diagram showing an operation state at the time of sample gas measurement. At this time, the first and third switching valves V1 and V3 have been switched to the connection states indicated by solid lines in FIG. The sample gas supplied at a constant flow rate from the sample gas inlet 13 passes through the first measuring pipe 14 and the second measuring pipe 19 as shown by arrows in FIG. At this time,
The carrier gas supplied via the first pressure controller 15 is discharged through the first pre-column PC1 and the first choke column CC1, and is discharged from the first dummy column DC1.
Through the first main column MC1. Thereby, components and the like adsorbed inside the first precolumn PC1 are carried away as described later. First and second measuring tubes 1
Reference numerals 4 and 19 denote, for example, loop tubes each having a predetermined volume, and ports g of the first and third switching valves V1 and V3.
A predetermined volume of sample gas is held between the port and the port j.

FIG. 5 is a flow path configuration diagram showing an operation state when a sample gas is introduced into a column. At this time, the first and third switching valves V1 and V3 are switched to the connection state shown by the dotted line in FIG. 3, and the second switching valve V2 is switched to the connection state shown by the solid line in FIG. The carrier gas supplied via the first pressure controller 15 flows through the first measuring pipe 14 in the reverse direction to push out the sample gas. The pushed sample gas is introduced into the first main column MC1 after passing through the first pre-column PC1. The first pre-column PC1 collects components of C3 or more (that is, C3, C4, C5, and C6 components). As a result, it is possible to remove an interference peak on the chromatogram and to prevent the second main column MC2 from deteriorating. While the sample gas from which such components have been removed passes through the first main column MC1,
A first group mainly composed of oxygen, nitrogen and methane,
It is separated into a second group mainly composed of carbon dioxide and ethane. When the sample gas contains hydrogen or carbon monoxide, these components belong to the first group. The components belonging to the first group that flowed out of the first main column MC1 earlier in time are introduced into the second main column MC2, separated into each component while passing through the second main column MC2, and separated into TCDs 22. Sent to

When a predetermined time has elapsed, the second switching valve V2 is switched to the connection state shown by the dotted line in FIG. The timing of this switching is set in advance so that the components belonging to the first group pass from the first main column MC1 until the components belonging to the second group start flowing out. Then, as shown in FIG. 6, the first main column M
The sample gas flowing out of C1 is introduced into the third main column MC3, separated into each component while passing through the third main column MC3, and sent to the TCD 22. Therefore,
In TCD22, each component is detected in the order of oxygen, nitrogen, and methane separated by the second main column MC2 first,
Next, each component is detected in the order of carbon dioxide and ethane separated by the third main column MC3, and a detection signal corresponding to the amount of each component is output. First to third main columns MC
By appropriately setting the separation conditions such as the length of 1 to MC3, the GC analysis time for each of these components, which conventionally required about 10 minutes, can be reduced to about 2 to 3 minutes.

Returning to FIG. 5, the description will be continued. The carrier gas supplied via the third pressure controller 17 flows through the second measuring pipe 19 in the reverse direction to push out the sample gas. The pushed sample gas is introduced into the fourth main column MC4 after passing through the second pre-column PC2. The second precolumn PC2 collects the C6 component. The third pressure controller 17 gradually increases the target set value of the pressure in a predetermined sequence, thereby increasing the supply flow rate of the carrier gas. While the sample gas passes through the fourth main column MC4, the C3, C4, and C5 components are clearly separated, but each component flows out while maintaining a clear separation by increasing the gas flow rate as described above. It is possible to reduce the time required to complete the process. The FID 23 detects the C3, C4, and C5 components sequentially introduced as described above, and outputs a detection signal corresponding to the amount. By using an alumina plot column as the fourth main column MC4 and concurrently controlling the pressure at the inlet of the column, the G3 of the C3 to C5 components conventionally required 15 minutes or more.
C analysis time can be suppressed within 3 minutes.

In this way, the GC analyzer 1 can obtain detection signals from the TCD 22 and the FID 23 in a short time. In the quantitative analysis unit 4, a chromatogram is created based on the detection signal obtained with the passage of time. 2A and 2B show an example of a chromatogram drawn when a certain city gas is measured by the present apparatus. FIG. 2A is a chromatogram based on the output of the TCD 22, and FIG. . As can be seen in FIG. 2, each component is clearly separated in a short analysis time.

At the time of actual analysis, a standard gas whose components and their concentrations are known in advance is introduced into the GC analyzer 1, and first, a reference chromatogram is created. Then, the peak area or height of each peak of the reference chromatogram is obtained, and a calibration curve showing the correspondence between these and the concentration is created.
Next, the fuel gas (sample gas) to be analyzed is supplied to the GC analysis unit 1.
Into a chromatogram, and determine the peak area or height of each peak. Then, the concentration Ci (%) of each component is calculated with reference to the calibration curve (where i represents each component).

At the time of measuring the standard gas and the sample gas, the atmospheric pressure monitor 8 measures the surrounding atmospheric pressure. The amount of gas stored in the first and second measuring pipes 14 and 19 of the GC analyzer 1 is affected by the fluctuation of atmospheric pressure. Therefore, the pressure correction unit 5 performs an operation of correcting the concentration Ci according to the ratio between the atmospheric pressure P1 at the time of measuring the standard gas and the atmospheric pressure P2 at the time of measuring the sample gas, and the concentration Ci ′ (% ) Is calculated.

The other component estimator 7 calculates the sum of the component concentrations Ci 'after the pressure correction. When all the components contained in the sample gas are the target components of the GC analysis,
The sum of the concentrations Ci 'should be 100%. However, if the sample gas contains components other than the analysis target, for example, components of C6 or higher, water, sulfur compounds, etc., these components are excluded from the above analysis, so that the concentration Ci 'Does not add up to 100%.
(Of course, generally supplied city gas hardly contains such non-analytical components.) Therefore, the difference between the total (%) of the concentrations Ci 'and 100% is the concentration or amount of the non-analytical components. This value can be used as one index value, and this value is calculated and output.

On the other hand, when the sum of the component concentrations Ci 'after the pressure correction deviates from 100%, the calorie calculator 6 calculates the component concentrations Ci' such that the sum becomes 100%.
Is calculated, and the normalized concentration C of each component is calculated.
i ″ is calculated. Then, the normalized concentration C of each component
i ″ is multiplied by a calorific value correction coefficient determined for each component, and the total is calculated to determine the total calorific value. Other arithmetic expressions may be used to calculate the total amount of heat.

FIG. 7 shows an example of the concentration-corrected concentration obtained by quantitative analysis of the chromatogram shown in FIG. 2 and the output result of the calculated calorific value. In this example, the sum of the concentrations of each component is 100.168%, which is extremely 100%.
It can be seen that all components contained in the sample gas are detected with almost no leakage and with high accuracy.

In the above embodiment, the calorific value of the sample gas was calculated. However, the fuel gas analyzer according to the present invention calculates various index values by a predetermined calculation based on the concentration of each component contained in the sample gas. It can be applied to anything that calculates. That is, the present invention is applicable to an apparatus that calculates a Wobbe index, a burning speed, a burning ability, and the like. Further, as the fuel gas that can be analyzed by the apparatus according to the present invention, hydrogen,
What is necessary is just what has oxygen, nitrogen, methane, carbon monoxide, carbon dioxide, and C3-C5 hydrocarbons as a main component.

[0031]

As described above, according to the fuel gas analyzer according to the present invention, the analysis time can be greatly reduced as compared with the conventional quantitative analysis method using a chromatograph. Therefore, for example, it is possible to measure the index value relating to the combustion of the supplied city gas without delay and with high frequency. In addition, since the concentration of each component is accurately obtained by gas chromatographic analysis and the index value is calculated based on the concentration, the index value can be obtained with high accuracy.
Even if a relatively large amount of components not to be analyzed are included in the gas chromatographic analysis, it is possible to know the state of the components. Therefore, it is possible to estimate the reliability of the calculated total calorific value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a fuel gas calorific value measuring apparatus according to an embodiment of the present invention.

FIG. 2 is an example of a chromatogram obtained by GC analysis of city gas.

FIG. 3 is a flow path configuration diagram of a GC analysis unit.

FIG. 4 is a flow path configuration diagram showing an operation state at the time of sample gas measurement.

FIG. 5 is a flow path configuration diagram showing an operation state when a sample gas is introduced into a column.

FIG. 6 is a flow path configuration diagram showing an operation state when a sample gas is introduced into a column.

FIG. 7 is an example of an output result of a concentration after pressure correction obtained by the apparatus of the present embodiment and a calorific value calculated.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 GC analysis unit 2 Detector 3 Data processing unit 4 Quantitative analysis unit 5 Pressure correction unit 6 Calorific value calculation unit 7 Other component estimation unit 8 Atmospheric pressure monitor 13 Sample gas inlets 14 and 19 Measuring tubes 15, 16, 17, 18 Pressure controller 22 Thermal conductivity detector (TCD) 23 Flame ionization detector (FID) V1, V3 Switching valve (10-port valve) V2 Switching valve ( PC1, PC2 ... Pre-column CC1, CC2 ... Choke column DC1, DC2, DC3 ... Dummy column MC1, MC2, MC3, MC4 ... Main column RC1 ... Reference column

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 30/46 G01N 30/46 A 30/48 30/48 H 30/62 30/62 B 30/68 30 / 68 A 30/86 30/86 J (72) Inventor Yasumasa Kamihara 1 Nishinokyo Kuwabaracho, Nakagyo-ku, Kyoto City Inside Shimadzu Corporation (72) Inventor Takeshi Ikeda 4-1-2, Hiranocho, Chuo-ku, Osaka-shi Inside Osaka Gas Co., Ltd. (72) Inventor Shuta Yuki 4-1-2 Hirano-cho, Chuo-ku, Osaka-shi Inside Osaka Gas Co., Ltd.

Claims (4)

[Claims] 1. a) a gas chromatograph for measuring the concentration of each component of the fuel gas; and b) measuring the atmospheric pressure at the time of fuel gas analysis, and determining the difference between the atmospheric pressure and the atmospheric pressure at the time of standard gas analysis. Pressure correction means for correcting the dependency of the concentration of each component obtained from the gas chromatograph on the amount of sample gas introduced, and c) a component other than the analysis target based on the sum of the analysis values of each component corrected by the pressure correction means. E) estimating means for estimating the amount of the component, d) arithmetic processing means for performing a predetermined arithmetic processing on the analysis value of each component corrected by the pressure correcting means to calculate an index value relating to the performance of the fuel gas, The gas chromatograph comprises: a1) introducing a sample gas into an independently provided measuring tube for analyzing a hydrocarbon component having 3 to 5 carbon atoms and other general components in parallel. Sample guide A2) a first separation section including a precolumn for removing hydrocarbon components having 3 or more carbon atoms, and a column for separating the components excluded by the precolumn; a3) a carbon column having 6 carbon atoms. A second column including a pre-column for removing the hydrocarbon components, an alumina plot column for separating the hydrocarbon components having 3 to 5 carbon atoms, and pressure control means for increasing the column inlet pressure in a predetermined sequence; A fuel gas analyzer, comprising: a separator; 2. The other general components include hydrogen, oxygen,
The fuel gas analyzer according to claim 1, wherein the fuel gas analyzer is nitrogen, methane, carbon monoxide, carbon dioxide, and ethane. 3. The first separation unit includes hydrogen, oxygen, nitrogen,
3. The fuel gas analyzer according to claim 2, wherein methane and carbon monoxide are separated from carbon dioxide and ethane in advance, and each component is separated by a different column. 4. The fuel gas analyzer according to claim 1, wherein the index value is a total calorific value.